Get current scene on Blender 2.74 using python
The issue with creating an object is where you are doing it, the scene's list of objects doesn't allow you to create new objects, only to link objects to the scene. To create a new object you use bpy.data.objects.new()

An example of manually creating a mesh object would be -

import bpy

# get the current scene
scn = bpy.context.scene

# create a mesh data block
mymesh = bpy.data.meshes.new('mymesh')

# define some vertices
verts = [Vector((-1,  1, 0)),
         Vector(( 1,  1, 0)),
         Vector(( 1, -1, 0)),
         Vector((-1, -1, 0)),
        ]

edges = []
faces = [[0, 1, 2, 3]]
# add the vertices to the mesh
mymesh.from_pydata(verts, edges, faces)

# create an object that uses the mesh data
myobj = bpy.data.objects.new('myobject', mymesh)

# link the object to the scene
scn.objects.link(myobj)